A very welcome expansion to one of the PC's finest real-time strategy games, Medieval Total War: Viking Invasion throws into the mix more factions, more units and a far stiffer challenge that in the original release. Requiring the original game to play, this time around the action focuses on the battles between the British and the Scandinavians some 1,200 years ago. And this is clearly a period of time the developers have had a lot of fun with. New units include the odd berserker, and on the weapons side, a nice cauldron of boiling oil isn't to be sniffed at. When you enter battle, things are better organised this time, primarily because you can sort your troops before and as hostilities commence. It's a big help; you can specify, for instance, the order in which the reinforcements arrive, while arranging those on the front line to maximum tactical advantage. That's the theory, anyway. Fundamentally, this game follows the tried and tested route of the expansion pack by pretty much leaving the main game intact. However, if you're after more of the same, then you're in business. That's because Medieval Total War: Viking Invasion presents an engrossing, long-lasting challenge, that genuinely offers excellent value for money. The developers could have got away with something that only added a few hours' worth of gameplay to the original, but instead Viking Invasion offers an awful lot more than that. That said, as with the original, you can aim criticism at the sadly inevitable slowdown when thousands of troops arrive on your screen, although things tick along without a murmur for the majority of the time. There's little doubt that Medieval Total War is an excellent game, and one of the finest ever seen on the PC. Its expansion pack is superb, marrying a terrific extra challenge with a bit more variety. --Simon Brew